1. Field of the Invention
This invention relates to a method of and apparatus for analyzing, e.g., measuring oxygen contact in the atmosphere of a combustion chamber, such as the type used for melting and/or fining glass.
2. Discussion of the Technical Problems
In the process of making a continuous flat glass ribbon, glass batch materials are conveniently moved into the upstream end of a heated combustion chamber. As the batch materials move downstream through the heated chamber, they melt to provide a pool of molten glass. The molten glass, as it advances through the heated chamber, is fined and the fined molten glass is continuously and controllably fed onto a pool of molten metal contained in a heated forming chamber. The molten glass, as it advances through the forming chamber, is controllably cooled and acted on to exit the forming chamber as a continuous glass ribbon of a given thickness and width.
The combustion chamber usually includes a regenerator at each of opposed chamber walls. The regenerators are usually elongated corridors which communicate with the chamber interior by way of a plurality of spaced ports in each of the opposed chamber walls. The interior of the regenerators usually includes a stacked arrangement of bricks, sometimes called "checker packing," which are heated by hot exhaust gases passing through the ports at one chamber wall and over the checker packing during one half of a heating cycle. During the remaining half of the heating cycle, combustion air passes over the heated checker packing through the ports past a fuel pipe mounted at the mouth of each port. The heated combustion air and combustion fuel from the pipes mix which results in flames issuing from the side of the chamber toward the chamber interior to heat same. With the above arrangement, as the packing of a regenerator at one side of the chamber is absorbing heat from the exhaust gases during one half of a heating cycle, the packing of the regenerator at the other side is heating incoming combustion air.
To maintain a high combustion efficiency and a chemical balance in the molten glass, the furnace atmosphere is monitored. In this regard, the exhaust gas is monitored to determine the percent of oxygen content therein. If the percent of oxygen contact in the chamber is above a predetermined level, the combustion may be considered to be incomplete, e.g., insufficient fuel moving through the fuel pipes, and if the oxygen content is below the predetermined level, there may be too much fuel moving through the fuel pipe resulting in wasting unignited fuel. In addition to monitoring oxygen content of the chamber atmosphere to determine combustion efficiency, oxygen content in the chamber atmosphere is also monitored because it can affect the fining process. For example, excess oxygen can cause excessive bubbles in the fined molten glass which results in excess voids in the formed glass ribbon. In addition, oxygen partial pressure in the chamber can affect the color of the formed glass ribbon. By way of illustration, oxygen partial pressure may be controlled to prevent undesirable oxidation of the iron or reduction of the iron or sulfur in the molten glass which can result in a yellowish green colored glass ribbon, a bluish tint in the glass ribbon, or an amber colored glass ribbon.
At present, there are available probes for monitoring oxygen content in the combustion chamber. One such probe is taught in U.S. patent application Ser. No. 227,015, filed on Jan. 21, 1981, in the names of E. P. Savolskis and T. L. Sanders, for "ATMOSPHERE SENSING DEVICE FOR A FURNACE" now U.S. Pat. No. 4,338,117, granted July 6, 1982. Although the probe is acceptable, there are limitations. For example, it is taught to mount the probe through a regenerator wall adjacent a port and above the checker packing to analyze the exhaust gases. However, in this position, the probe is mounted in an area of negative pressure relative to the pressure of the ambient atmosphere. This results in drawing air from the furnace exterior through openings, e.g., cracks in the port or regenerator walls which can dilute the sample of chamber atmosphere being analyzed.
As can now be appreciated, it would be advantageous to provide a method of and apparatus for sensing oxygen content in the atmosphere of a glass melting and/or fining furnace of a flat glass melting apparatus that eliminates the limitations of the presently available techniques.